Carbon reamer handle

ABSTRACT

A reamer for use in minimally invasive hip replacement surgical approaches is provided. The reamer spindle includes an offset elongate housing portion that extends from a proximal housing end portion a distal housing end portion. A handle assembly, preferably comprising a durable lightweight material such as carbon fiber that is removably connectable to the housing of the reamer spindle. A reamer head is removably connectable to the distal neck portion and has a surface configured to cut bone.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. utility applicationSer. No. 13/290,202, filed on Nov. 7, 2011, now U.S. Pat. No. 9,078,672which claims priority to U.S. provisional application Ser. No.61/410,418, filed on Nov. 5, 2010.

BACKGROUND OF THE INVENTION

Nearly 200,000 hip replacements are performed each year in the UnitedStates and the number is expected to continue to grow as the populationages. The usual reasons for hip replacement are osteoarthritis,rheumatoid arthritis and traumatic arthritis, all of which can causepain and stiffness that limit mobility and the ability to perform dailyliving activities. Hip replacement surgery is usually performed whenother measures (e.g., physical therapy, medications, and walking aids)are unable to overcome the chronic pain and disability associated withthese conditions.

Various techniques are used by orthopedic surgeons to perform hipreplacements. These include the following approaches: anterior,antero-lateral, anterior, posterior, and postero-lateral. The posteriorand posteolateral approaches account for approximately 60% to 70% of hipreplacement surgeries.

Traditional hip replacement surgery involves an open procedure andextensive surgical dissection. However, such procedures require a longerrecovery period and rehabilitation time for the patient. The averagehospital stay for open hip replacement procedures is 4-5 days, followedin most cases by extensive rehabilitation.

More recently, there has been considerable interest and research done inMinimally Invasive Surgery (MIS), including the use of MIS procedures inconnection with hip replacement surgery. In comparison with thetraditional open surgical approach, MIS hip replacement surgeriesinvolve fewer traumas to the muscles surrounding the hip joint.Specifically, fewer muscles that help to stabilize the hip joint are cutin MIS hip replacement surgeries, reducing the risk of dislocation ofthe hip surgery and speeding recovery. Patients spend less time in thehospital and return to normal life activities more quickly.

MIS approaches use smaller surgical fields, which require smallerinstruments to perform the hip replacement procedures. One suchinstrument is a reamer spindle detachably connected to a surgicalreamer. The surgical reamer is used to shape the bone of the acetabulum.However, reamer spindles have typically been straight with a handle in afixed orientation. These prior art reamer spindles are not ideal for MISapproaches. The straight design and fixed handle orientation impedes thetool's ability to be used in small, tortuous spaces within the body,particularly of MIS procedures.

Accordingly, there is a need for an improved reamer spindle for use inMIS hip replacement surgical approaches. The present invention providesa reamer spindle with an offset reamer position and a handle that isable to be positioned in a multitude of orientations. These features ofthe reamer spindle of the present invention address previousshortcomings of previous reamer spindles, particularly for use in MISprocedures.

SUMMARY OF THE INVENTION

In accordance with one embodiment, a reamer for use in minimallyinvasive hip replacement surgical approaches is provided- The reamerspindle includes a housing with offset proximal and distal end portions.Specifically, the reamer spindle comprises an elongate housing portionthat extends along a first longitudinal axis and a neck or distalportion that extends along a second longitudinal axis. A reamer head isremovably connectable to the distal neck portion and has a surfaceconfigured to cut hone.

In accordance with another embodiment, the reamer spindle comprises aremovable handle that is composed of a durable light weight materialsuch as carbon fiber. The handle is designed such that it can be easilyremoved and positioned in multiple orientations about the proximal endportion of the spindle.

In accordance with still another embodiment, the elongate housingportion meets the distal neck portion at a rounded low profile surfaceconfigured to inhibit trauma to muscle tissue during use of the reamerspindle.

In accordance with yet another embodiment, the reamer can be driven by asource of rotational power, which may be an electric source. The housingis configured to enclose a rotatable shaft connectable to the reamerwith the proximal end of the shaft being removably connectable to thesource of rotational power. The housing may he composed of a polymersuch as a durable lightweight carbon fiber material, a metal (e.g.,stainless steel), super alloy or composite casing.

In accordance with another embodiment, the reamer spindle is configuredin a way that it can be sterilized between uses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of the reamer spindle of the presentinvention.

FIG. 2 shows an exploded view of the components comprising the reamerspindle.

FIG. 3 shows a magnified view of an embodiment of the housing assemblyof the present invention.

FIG. 4 illustrates a magnified view illustrating an embodiment ofattaching the handle assembly to the housing.

FIG. 5 is a cross-sectional view of an embodiment of the handle assemblyconnected to the housing.

FIG. 6 shows a cross-sectional view of an alternate embodiment of thehandle assembly connected to the housing.

FIG. 7 illustrates embodiments of various orientations of the handleassembly with respect to the housing.

FIG. 8 is a cross-sectional view of a portion of the drive trainresiding within the housing.

FIG. 9 is an exploded view of the components that comprise the drivetrain of the present invention.

FIG. 10 is a magnified view of an embodiment of the distal end of thereamer spindle of the present invention.

FIG. 11 is an exploded and enlarged view showing the connectionstructure of the distal U-joint 128 to a reamer connection crown 140.

FIG. 12 is an enlarged perspective view of the distal U-joint 128 andconnection crown 140 in a closely spaced relationship with a reamer 12shown in phantom attached. thereto.

FIGS. 13 to 15 are schematic views of the anatomy of a human hip joint.

FIG. 16 is a block diagram illustrating steps in a minimally invasivehip replacement surgery using a posterior approach.

FIG. 17 is a schematic view of the orientation of the reamer spindle 10during use in a minimally invasive hip replacement surgery.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings, FIGS. 1 and 2 illustrate a reamer spindle10 according to the present invention. The reamer spindle 10 isconnectable to a reamer 12 (FIG. 12) for performing a minimally invasivehip replacement surgery. The reamer spindle 10 generally comprises adrive train 14 disposed within a housing 16. A handle assembly 18 isadjustably connected to the housing 16 spaced from the reamer 12.

The housing 16 has a length that extends from a proximal end portion toa distal end portion. Specifically, the housing 16 extends from a mainhousing section 20, located at the proximal end portion, to a distalneck section 22 with an intermediate housing section 24 therebetween. Anopening 26 resides within the housing that extends from the main housingsection 20 through the distal neck section 22.

The main housing section 20 further comprises a proximal main housingportion 28, a distal main housing portion 30 and a central main housingportion 32 therebetween (FIG. 2). As shown in FIG. 1, the main housingsection 20 extends along longitudinal axis A-A.

As shown in FIG. 7, the distal main housing portion 30 comprises spacedapart right and left side walls 34A and 34B extending upwardly from abottom wall 34C to a top wall 34D. In a preferred embodiment, the rightand left side walls 34A and 34B fluidly transition to a top wall 34D.This construction provides the distal main housing portion 30 with agenerally rectangular-shaped cross-section. In a further preferredembodiment, the top wall 34D has a beveled top surface.

The central main housing portion 32 resides proximally of the distalmain housing portion 30. The right and left side walls 34A, 34B and thebottom and top walls 34C, 34D of the distal main housing portion 30,extend proximally to form the walls of the central main housing portion32. Similarly to the distal main housing portion 30, the central mainhousing portion 32 has a generally rectangular-shaped cross-section. Ina preferred embodiment, the central housing portion 32 has a greaterwidth and height as compared to the distal main housing portion 30.

In a further preferred embodiment, a first frustro-conical transitionportion 36 resides between the distal main housing portion 30 and thecentral main housing portion 32. The first frustro-conical transitionportion 36 forms a fluid transition between the distal main housingportion 30 and the central main housing portion 32. A secondfrustro-conical transition portion 38 (FIG. 4) resides between thecentral main housing portion 32 and the proximal main housing portion28. The second frustro-conical transition portion 38 forms a fluidtransition between the central portion 32 and the proximal main housingportion 28.

The proximal main portion of the 28 of the main housing section 23resides proximally of the central main housing portion 32. The proximalmain portion 28 further comprises an annular extension 40 (FIG. 4) thatextends proximally from the second frustro-conical transition portion28. The extension has an annular wall 42 with a curved cross-section.More preferably, the extension 40 comprises a circular cross-section.Although a circular cross-sectional geometry is preferred, the extensionmay comprise any of a non-limiting geometry including a rectangular, ahexagon, a triangular or the like. In a preferred embodiment, theannular extension wall 42 has an outer diameter 44 ranging from about 15mm to about 20 mm, an inner diameter 46 ranging from about 10 mm toabout 15 mm, and an extension throughbore 48 therebetween. The extensionfluidly extends proximally from a larger diameter second frustro-conicaltransition portion 38 to the smaller diameter of the annular extensionwall 42. The throughbore 48 preferably extends co-axially with thelongitudinal axis A-A.

A series of extension openings 50 are preferably positioned through theannual wall of the housing extension 42. In a preferred embodiment, fouropenings 50 are positioned through the annular wall 42 of the extension40. The openings 50 are positioned circumferentially around theextension 40 such that they are oriented about perpendicular from eachother. It should be noted that the reamer spindle 10 may be designedwith more or less than four openings and that they may be positionedanywhere along the surface as shown in FIG. 4. As will be discussed inmore detail, these openings 50 form a means of attachment of the handleassembly 18 to the housing 16.

As shown in FIG. 1, the intermediate housing section 24 extends distallyfrom the main housing section 20 and proximally from the distal necksection 22. The intermediate housing section 24 comprises spaced apartright and left side walls 52A and 528 extending upwardly from a bottomwall 52C to a top wall 52D. This construction provides the intermediatesection 24 with a generally rectangular-shaped cross-section. In apreferred embodiment, an intermediate housing opening 54 may bepositioned through the bottom wall 52C of the intermediate section 24(FIG. 8). More preferably, this opening 54 may extend through the bottomwall of the intermediate housing section 24 and a portion of the distalmain housing portion 30. A removable access cover 56 (FIG. 2) may bepositioned over the opening 54. This access cover 56 prohibits debrisfrom entering the housing 16 and provides easy access for cleaning thedrive train 14 therewithin.

As shown in FIGS. 1 and 2, the distal end of the intermediary section 24fluidly extends distally into the distal neck section 22. In a preferredembodiment, the distal neck. section comprises a distal annular wall 58with an outer diameter ranging from about 15 mm to about 2 mm, an innerdiameter ranging from about 10 mm to about 15 mm, and a distal neckopening 60 therethrough. At the opposite end, the proximal end of theintermediate housing section 24 fluidly transitions into the distal end30 of the main housing section 32. The left and right side walls 52A,52B and the bottom and top walls 52C, 52D of the intermediary section 24fluidly transition proximally into the distal main housing portion 30.

The intermediate housing section 24 is angled from the main housingsection 32. An intermediate housing angle 62 is formed between. theintersection of an imaginary line C-C that extends tangentially along abottom surface 64 of the intermediate housing section 24 andlongitudinal axis A-A (FIG. 1). In a preferred embodiment, theintermediate housing angle 62 ranges from about 20° to about 40°, morepreferably, the intermediate housing angle 62 is about 30°. Theintermediate housing section 24 forms an offset between the main housingsection 32 and the distal neck section 22 which extends parallel alonglongitudinal axis B-B. In a further embodiment, an offset distance 66between longitudinal axes A-A and B-B ranges from about 2 cm to about 5cm.

It should be noted that it is preferred that the different sectionscomprising the housing 16 of the reamer spindle 10 are constructed suchthat they fluidly transition into each other. The distal neck section 22transitions into the intermediate section 24 which transitions into themain housing section 32. The side walls 52A, 52B, top wall 52C, andbottom wall 52D of the intermediate housing section 24 extend distallyto the distal neck section 22 of the spindle 10.

As shown in FIGS. 1 and 3 to 6, the handle assembly 18 of the presentinvention comprises a handle head portion 66 and a handle grippingportion 68. The handle head portion 66 is positioned about perpendicularto the handle gripping portion 68. The handle head portion 66 isconstructed such that it is removably connectable to the curved housingextension portion 40 residing at the proximal end of the main housingsection 32. The handle assembly 18 is composed of a durable lightweightmaterial such as a polymeric material. More preferably, the handleassembly 18 may be composed of carbon fiber.

The handle head portion 66 comprises a distal handle head portion 70spaced apart from a proximal handle head portion 72, a handlethroughbore 74 extends therebetween. The handle head portion 66 furthercomprises a right handle wall 76A spaced apart from a left handle wall76B. A bottom handle wall 76C is spaced apart from a top handle wall760. This construction provides the handle head portion 72 with agenerally rectangular cross-section.

In a preferred embodiment, the handle throughbore 74 has a curvedcross-section and more preferably has a round cross-section. Thethroughbore 74 is preferably dimensioned such that the housing extension40 is positionable therewithin. In a preferred embodiment, the housingextension 40 is advanced through the handle throughbore 74.

The proximal end of the handle head portion 72 comprises an annularrecess 78 that is designed to be fitted to the second frustro-conicaltransition portion 38 of the main housing section 32. When the handleassembly 18 is positioned over the housing extension 40, the handle headportion 66 is positioned about parallel to longitudinal axis A-A.Furthermore, the left and right walls as well as the top and bottomwalls of the main housing section 32 and the handle head portion 66 arefitted about parallel to each other.

A pin 80, residing within the handle head portion 66, is designed to bepositioned within one of the openings 50 of the housing extension 40.The pin 80, which is preferably positioned about perpendicular tolongitudinal axis A-A, is attached to a distal end potion 82 of a handlelever 84. The handle lever 84 further comprises a lever proximal endportion 86 that is spaced from the distal end portion 82 of the handlelever 84. The proximal end portion 86 of the handle lever 84 comprises athumb recess 88 within its outer surface. In a preferred embodiment, twopins 80, each residing at the distal ends of their respective handlelevers 84, are positioned opposing each other. This preferred pinorientation enables the handle assembly 18 to be in a more secureengagement with the housing 16.

As shown in FIGS. 3, 5, and 6, each handle lever 84 pivots about ahandle pin 90 that resides between the distal 82 and proximal endportions 86 of the handle lever 84. The pin 90 is further positionedthrough the thickness of the lever 84, perpendicular to longitudinalaxis A-A.

A spring 92 is preferably positioned between the body of the handle headportion 66 and the proximal end portion of the handle lever 84. Thespring 92 is further positioned such that one end of the spring 92resides within a recess 94 disposed within an inner surface of theproximal end portion 86 of the handle lever 84. The opposite end of thespring 92 resides in a recess 96 within an outer surface of the body ofthe handle head portion 66. The spring 92 acts as a bias between theinner surface of the proximal end portion of the handle lever 84 and thebody of the handle head portion 66.

The handle assembly 18 is designed such that when a force is applied tothe proximal end portion 86 of the handle lever 84, such as by pressingthe lever with a thumb, the proximal lever end moves towards the outersurface of the handle head portion 66. Specifically, when the force isapplied to the proximal end, the lever 84 pivots about the handle pin 90such that the distal end 82 of the lever moves in an opposite directionof that of the lever's proximal end. The distal end 82 of the lever 84moves away from the outer surface of the handle head portion 66 as shownin FIG. 6. Since the lever pin 80 is connected to the distal end portion82 of the handle lever 84, the pin 80 is pulled out of the extensionopening 50 and moves within the wall thickness of the handle headportion 66. At the same time, the proximal end 86 of the handle levers84 moves through respective lever cutout portions 98 to enableunobstructed movement and full pivoting action of the handle levers.

Thus, the handle assembly 18 can be positioned such that the extension40 of the main housing section 32 is positioned within the throughbore74 of the handle head portion 66. Once the extension is positionedwithin the throughbore 74, the force applied to the proximal end portionof the handle lever 84 is released, thereby allowing the lever pin 80 tomove proximally towards the housing extension 40. The spring 92 providesthe biasing force against the proximal end portion of the handle lever84 that returns the lever 84 to its initial position, about parallel tolongitudinal axis A-A.

In a preferred embodiment, when the lever is returned to its initialposition, the lever pin 80 extends past an inner wall surface 100 of thehandle head portion 66. Furthermore, the pin 80 is positioned throughone of the openings 50 of the housing extension 40, engaging the handleassembly 18 therewithin. Once the lever pin 80 is positioned within theopening 50 of the extension 40, the handle assembly 18 is in a lockedrelationship with the housing 16 of the spindle 10. The handle assembly18 can be disengaged from the housing 16 of the spindle 10 by depressingthe proximal end portion 86 of the handle lever 84 as shown in FIG. 6.The handle lever 84 therefore, enables the pin 80 to pivot out of theextension opening 50 and disengage the handle assembly 18 from thehousing 16.

The handle assembly 18 can be positioned in a multitude of non-limitingorientations with respect to the main housing section 32. In a preferredembodiment, the handle assembly 18 can be positioned at 90° intervalsabout the circumference of the housing extension 40 as shown in FIG. 7.In a preferred embodiment, the opposing pins 80 of the handle assembly18 are positioned within opposing openings 50 that extends through theannular wall 42 of the housing extension 40.

As previously mentioned, the drive train 14 resides within the housing16 of the reamer spindle 10 of the present invention. A series ofbrackets 102 (FIGS. 2 and 8) may be used to hold the drive train 14 inplace within the housing 16. In a preferred embodiment, the drive train14 extends from the distal neck portion 22 through the proximal endportion of the housing extension 40.

As particularly shown in FIGS. 8 and 9, the drive train 14 comprises aseries of interconnected U-joints, pivot blocks and pins in a pivotablerelationship. A drive shaft 104 as a cylindrically-shaped member havinga proximal portion 104A and a distal end portion 104B with a lengththere between is in a releasable connection with the drive train 14. Theproximal shaft portion 104A comprises a series of cylindrical sections106A, 106B and 106C that step down in diameter as they progress towardthe proximal end 104A of the shaft 104. In a preferred embodiment,cylindrical section 106B has a hexagonal or similar type structure thatprovides flats for detachable connection to the chuck of a source ofrotary drive power (not shown).

As illustrated in FIGS. 1, 2, and 9, the drive shaft 104 is positionedabout parallel or co-axially to longitudinal axis A-A, with a portion ofits proximal end extending proximally past the handle assembly 18. Theproximal portion 104A of the drive shaft 104 also comprises a sleeve 108(FIG. 8) that is positioned distal of the series of cylindrical sections106A, 106B, and 106C. In a preferred embodiment, the sleeve ispositioned about the circumference of the shaft 104 such that it is incontact with the end of the annular wall 42 of the housing extension 40.The sleeve 108 is further constructed such that it is in a rotatablerelationship about the shaft 104. The sleeve is preferably constructedof a polymeric material that provides mechanical wear resistance.Although a polymeric material is preferred, other materials such asmetal or ceramic may also be used to construct the sleeve 108.

The distal end 104B of the drive shaft 104 comprises a hexagonal orsimilar structure that provides flats for detachable connection to thedrive train 14. In a preferred embodiment, the distal end 104B of thedrive shaft 104 is in a detachable connection with a socket end 110 ofthe drive train residing with the housing 16.

As particularly shown in FIGS. 8 and 9, a first or proximal U-joint 112is supported at the distal end 104B of the shaft 104. In a preferredembodiment, the distal end 104B of the shaft 104 engages within thesocket end 110 of the first or proximal U-joint 112. The proximalU-joint 112 is further comprised of a proximal cylindrical side wall112A supporting a pair of yoke plates 1123 and 1120 having respectiveopenings 112D, 112E.

A second U-joint 114 is positioned distal of the first U-joint 112. Thesecond U-joint comprises a second side wall 114A supporting a pair ofyoke plates 114B, 114C. The second U-joint 114 is positioned such thatits pair of yoke plates 114B, 114C oppose the yokes plates 112B, 112C ofthe first U-joint 112. A proximal pivot block 116 (FIG. 9) residesbetween the yoke plates 112B, 112C of the proximal U-joint 112 and thepair of yoke plates 114B, 114C of the second U-joint 114. The proximalpivot block 116 comprises two pairs of perpendicularly opposed openings116A and 116B.

Pins 118A are received in the openings 112D, 112E in the yoke plates112B and 112C of the proximal U-joint 112 and the opening 116A in thepivot block 116, and a pin 116B is received in the opening 116B of thepivot, block 116 and the openings 114D, 114E of the yoke plates 114B,114C of the second U-joint 114 to thereby pivotably secure the proximalU-joint 112 to the second U-joint. 114. It is noted that only one of thepins 118A or 118B extends completely from one face of the pivot block116 to the other face. As passage from one face to the other is blockedby the first pin, the other of the two pins 118A or 118B is two “halfpins”.

As shown in FIG. 9 the drive train 14 also includes a third U-joint 120that comprises a third cylindrical side wall 120A supporting a pair ofyoke plates 120B and 120C having respective openings 120D, 120E. Thethird U-joint 120 is positioned such that a third U-joint receiving end122 opposes a receiving end. 124 of the second U-joint 114. Anintermediary rod 126 is positioned between the second and third U-joints114, 120, preferably within the respective receiving ends 122, 124.

The drive train 14 comprises a distal or fourth U-joint 128 that ispositioned distal of the third U-joint 120. The distal U-joint 128comprises a distal sidewall 128A supporting a pair of yoke plates 128B,128C and is further positioned such that its pair of yoke plates 128B,128C oppose the yokes plates 120B, 120C of the third U-joint 120. Adistal pivot block 130 (FIG. 9) resides between the yoke plates 120B,120C of the third U-joint 120 and the pair of yoke plates 128B, 128C ofthe fourth U-joint 128. The proximal pivot block 130 comprises two pairsof perpendicularly opposed openings 130A and 130B.

Pins 132B, 132C are received in the openings 128D, 128E in the yokeplates 128B and 128C of the distal U-joint 128 and the opening 130A inthe distal pivot block 130, and a pin 132A is received in the opening130B of the distal pivot block 130 and the openings 120D, 120E of theyoke plates 120B, 120C of the third U-joint 120 to thereby pivotablysecure the third U-joint 120 to the distal U-joint 128. Opposite theyoke plates, the cylindrical side wall 128A meets a base plate 134having an enlarged diameter. A plurality of pins 136 extending outwardlyfrom the base plate 134 have their respective axes aligned parallel toeach other.

In this manner, the drive train 14 comprising the drive shaft 104, thefirst U-joint. 112, the first pivot block 116, the second U-joint 114,the intermediary rod 126, the third U-joint 120, the distal pivot block130 and the proximal U-joint 128 provides for transmission of rotationalmotion imparted to the proximal end of the shaft 104 to the base plate134 and its supported pins 136.

As particularly shown in FIG. 11, the base plate 134 of the proximalU-joint 128 includes a central opening 138 completely through thethickness of the plate. A reamer connection crown 140 comprises a baseplate 140A supporting a plurality of angled fingers 140B. Preferably,there are four angled fingers 140B. The plate 140A is provided withopenings 142 that receive the pins 136 extending from the base plate 134of the proximal U-joint 128.

An abutment pin 144 is a cylindrically shaped member having a firstsection 144A of a lesser diameter, an intermediate section 144B of anintermediate diameter and a larger diameter third section 144C. A coilspring 146 is received on the abutment pin 144 surrounding theintermediate section 144B. The spring 146 abuts against the thirdsection 144C. The first section 144A of the pin 144 is received in acentral opening 148 in the base 140A of the reamer connection crown 140in a fixed manner.

One end of the coil spring 146 biases against the base plate 134 ofdistal U-joint 128. That is on the side of the plate 134 opposite thepins 136. The other end of spring 146 biases against the larger diametersection 144C of pin 144. However, since the first section 144A of thepin 144 is fixed to the base 140A of the crown 140, the crown is therebytensioned. into a secured relationship with the distal U-joint 128. Thebias of spring 146 enables the distance between the connection crown 140against the distal U-joint 128 to be manipulated between aclosely-spaced relationship and a spaced apart position.

In that manner, the reamer 12 is removably fixed to the drive train 14by manipulating the reamer connection crown 140 in an axial directionaway from the distal U-joint 128 and against the biasing force of thespring 146. This creates separation between the crown 140 and theU-joint 128, which prior to manipulation are in the closely-spacedrelationship, and removes the pins 136 from blocking access to thespaces 150 provided between the fingers 140B and the crown plate 140A.The connection structure, such as the cross-bars 152 (FIG. 12) of thereamer 12, is then. capable of being received in these spaces 150. Whenthe surgeon releases his grip on the crown 140, the spring 146 returnsthe connection crown to its original closely-spaced relationship againstthe plate 134 of the distal U-joint 128. The pins 136 are once againpartially residing in the spaces 142 between the fingers 140B and thebase plate 140A to thereby prevent unintended release of the reamer 12from the drive train 14 of the reamer spindle 10. This connectionstructure is commonly referred to as a “bayonet-type” connection.

FIGS. 13 to 15 depict some features of the musculoskeletal anatomy of ahuman hip region. As shown in FIG. 13, there are several muscles thatact to stabilize the femoral head of a femur bone in the acetabulum.Those include the short external rotator muscles (i.e., the piriformis,the superior gemellus, the obturator internus, the inferior gemellusobturator externus and the quadratus femoris). The gluteus maximus (seeFIG. 14) extends over the short external rotator muscles. The femoralhead is enclosed in a fibrous capsule (see FIG. 15), which attaches tothe bone outside the acetabular lip and to the base of the neck of thefemoral head.

The MIS posterior hip replacement approach has traditionally involvedfirst a skin incision, followed by an incision in the fascia lata, andthen detachment of the short external rotator muscles of the hip (seeFIG. 13). However, in a modified MIS posterior hip replacement approach,described further below, only the piriformis muscle or conjoined tendonneeds to be detached.

FIG. 16 is a schematic block diagram illustrating steps in a method 200for using the reamer spindle 10 in a MIS hip replacement surgery. Thesurgeon begins by making an incision 210 in a posterior side of apatient's hip (e.g., on the buttocks) on a side proximate the hip jointto be treated. The surgeon then separates 220 fibers in the gluteusmaximus longitudinally (i.e., not cut transversely) using a transmaximus approach to access the capsule. The present approach does notinvolve an incision in the fascia lata, which is required in otherposterior surgical approaches. The surgeon then detaches 230 thepiriformis or conjoined tendon, which, is the only short externalrotator muscle that is detached. This approach preserves the superiorgemellus if it is not conjoined to the pirif tendon, obturator internus,inferior gemellus obturator externus and quadratus femoris, whichprovide significant additional stability to the hip. It is believed thatsuch preservation also facilitates significantly faster post operativerecovery. The surgeon then performs a capsulotomy 240 (e.g., L-shape orJ-shape) to access the acetabulum. Once access to the acetabulum isachieved, the surgeon advances 250 the distal section 22 of the reamerspindle 10 supporting the reamer 12 through the incision to the surgicale proximate the acetabulum (see FIG. 17). The reamer spindle 10 is nowoperated to cut bone from the acetabulum (e.g. diseased bone) andprepare the acetabulum for implantation of a prosthetic acetabular cup.The femoral head is also removed and a prosthetic hip stem implantedinto the femur, the prosthetic hip stem having a femoral ball headconfigured to articulatingly couple to the acetabular cup prosthesis.Once the prosthesis is in place, the capsule can be closed 260, followedby closure in the incisions to the gluteus maximus and skin.

The reamer spindle 10 is preferably configured for reuse, and can bedisassembled for sterilization between uses. Disassembly is done byfirst depressing the handle lever 84 which disengages the pin or pins 80from the opening 50 of housing extension 40. Once the handle assembly 18is removed, the drive shaft 104 can be removed from the drive train 14within the housing 16. After the drive shaft 104 is removed, the accesspanel 56 may be removed which allows access to the components comprisingthe drive train 14. Once the access panel 56 is removed, the reamerspindle 10 can be sterilized for reuse.

Additionally, the housing 16 is preferably made of a durable materialthat can be washed and sterilized (e.g., with high heat) to comply withsterilization standards known in the art. In one embodiment, the housing16 is made of metal, such as stainless or a super alloy material. Inanother embodiment, the housing 16 is made of a composite material suchas carbon fiber. Though the illustrated embodiment shows the housing 16as being one piece, in other embodiments it can be modular to facilitatedisassembly of the reamer spindle 10.

Preferably, the reaming angle should correlate as closely as possible tothe intended angle of acetabular cup implantation.

Additionally, as discussed above, the length of the distal neck section22 is preferably between about 25 mm and about 35 mm. This range isparticularly advantageous in MIS hip replacement surgical procedures(e.g., the method illustrated in FIG. 16) in that during the surgicalprocedure the distal neck section 22 is in direct contact with the shortexternal rotator muscles, which must be preserved to optimize theclinical outcome. The length of approximately 25-35 mm advantageouslyallows the reamer 12 to be positioned within the acetabulum whileminimizing contact between the reamer spindle 10 (e.g., the distal necksection 22) and the short external rotator muscles of the hip, which arein the inferior aspect of the wound. Additionally, the thickness (e.g.,outer diameter) of the housing 16, which is preferably between about 9mm and about 16 mm also advantageously minimizes soft tissue traumaduring advancement of the reamer spindle 10 through the incision toposition the reamer 12 within the acetabulum.

Through the reamer spindle 10 is discussed above in connection with anMIS hip replacement posterior approach, one of the ordinary skill in theart will recognize that the reamer spindle 10 can be used in other MIShip replacement surgical approaches, such as the anterior,antero-lateral, and postero-lateral approaches. Additionally, the reamerspindle 10 may also be usable in applications other than posterior MIShip replacement procedures such as interior, interior-lateral andpostero-lateral approaches, as well as shoulder replacement procedures.Though use of the reamer spindle 10 is described herein with respect tohuman hip replacement surgery, one of ordinary skill in the art willrecognize that it may also be useful in animal hip replacementsurgeries.

Of course, the foregoing description is that of certain features,aspects and advantages of the present invention, to which variouschanges and modifications can be made without departing from the spiritand scope of the present invention. Moreover, the reamer need notfeature all of the objects, advantages, features and aspects discussedabove. For example, in some embodiments, the casing of the reamer in theneck portion can be removed and/or replaced with a shield member toinhibit trauma to muscle tissue during operation of the reamer. Thus,for example, those of skill in the art will recognize that the inventioncan be embodied or carried out in a manner that achieves or optimizesone advantage or a group of advantages as taught herein withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein. In addition, while a number of variations of theinvention have been shown and described in detail, other modificationsand methods of use, which are within the scope of this invention, willbe readily apparent to those of skill in the art based upon thisdisclosure. It is contemplated that various combinations orsubcombinations of these specific features and aspects of embodimentsmay be made and still fall within the scope of the invention.

What is claimed is:
 1. A handle assembly, comprising: a handle headportion supporting a handle grip, wherein the handle head portiondefines a throughbore that extends along a first longitudinal axis thatreceives at least a portion of a tool; b) a locking mechanism supportedby the handle head portion comprising a lever pivotably supported by apivot pin secured to the handle head portion, wherein the lever extendsalong a second longitudinal axis from a proximal lever portion to adistal lever portion, and wherein the second longitudinal axis is spacedfrom the first longitudinal axis; and c) wherein the proximal leverportion is pivotably manipulatable about the pivot pin to provide acontactable relationship of the distal lever portion with at least aportion of a surface of the tool when inserted within the handle headportion throughbore to thereby provide the handle grip supported by thehandle head portion in a lockable position with at least a portion ofthe tool inserted within the throughbore.
 2. The handle assembly ofclaim 1 wherein the proximal lever portion is further manipulatableabout the pivot pin to move the distal lever portion away from the toolsurface to thereby permit removal of the tool from the handle headportion.
 3. The handle assembly of claim 1 wherein a spring ispositioned between the handle head portion and the proximal leverportion to thereby provide a bias against the proximal lever portion. 4.The handle assembly of claim 1 wherein a lever pin extends from thedistal lever portion, the lever pin extending inwardly toward the firstlongitudinal axis.
 5. The handle assembly of claim 4 wherein the leverpin is registerable with an opening that at least partially extendsthrough the surface of the tool.
 6. The handle assembly of claim 1wherein the tool is selected from the group consisting of a drive shaft,a rod, a tube, a drive train, and an orthopedic reamer spindle.
 7. Thehandle assembly of claim 1 wherein the distal lever portion iscontactable with the surface of a tool housing.
 8. The handle assemblyof claim 1 further composed of a polymeric material.
 9. The handleassembly of claim 1 further composed of a carbon fiber material.
 10. Ahandle assembly, comprising: a) a handle head portion supporting ahandle grip, wherein the handle head portion defines a throughbore thatextends along a first longitudinal axis that receives at least a portionof a tool; b) a locking mechanism supported by the handle head portion,the locking mechanism comprising: i) a lever pivotably supported by apivot pin secured to the handle head portion, wherein the lever extendsalong a second longitudinal axis from a proximal lever portion to adistal lever portion, and wherein the second longitudinal axis is spacedfrom the first longitudinal axis of the main housing section; ii) alever pin at the distal lever portion, the lever pin extending inwardlytoward the first longitudinal axis; and iii) a spring positioned betweenthe handle head portion and the proximal lever portion; and c) whereinthe proximal lever portion is pivotably manipulatable about the pivotpin and against a bias of the spring so that the lever pin is in acontactable relationship with a surface of the tool when at leastpartially inserted within the throughbore to thereby provide the handlegrip supported by the handle head portion in a removably lockableposition with respect to the first longitudinal axis of the handle headportion.
 11. The handle assembly of claim 10 wherein the proximal leverportion is further manipulatable about the pivot pin and against thebias of the spring to move the lever pin away from the surface of thetool to thereby permit removal of the tool from the handle head portion.12. The handle assembly of claim 10 wherein the tool is selected fromthe group consisting of a drive shaft, a rod, a tube, a drive train, andan orthopedic reamer spindle.
 13. The handle assembly of claim 10wherein the proximal lever portion is further manipulatable about thepivot pin and against the bias of the spring to register the lever pinwith a first opening that at least partially extends through the surfaceof the tool to thereby create a lockable relationship therebetween. 14.The handle assembly of claim 13 wherein the proximal lever portion isfurther manipulatable about the pivot pin and against. the bias of thespring to remove the lever pin from the first opening to thereby permitrelative rotational movement of the handle grip connected to the handlehead portion about the tool until the lever pin is aligned with a secondopening that at least partially extends through the surface of the tooland then the proximal lever portion is manipulatable to cause the springto bias the lever pin into registry with the second opening to therebyprovide, with respect to the first longitudinal axis of the handle headportion, the handle grip in a second locked position different than afirst locked position.
 15. The handle assembly of claim 10 furthercomposed of a polymeric material.
 16. The handle assembly of claim 10further composed of a carbon fiber material.
 17. The handle assembly ofclaim 10 wherein the lever pin is contactable with the surface of a toolhousing.